The present invention generally relates to fenestration products, e.g., windows. In particular, aspects of the invention relate to prefabricated fenestration frame assemblies and methods of installing such assemblies in a fenestration.
Increasingly, prefabricated fenestration products, i.e., prefabricated doors and windows, are used both in new construction and in renovation of existing buildings. Prefabricated fenestration products typically are formed for walls having a fixed thickness. If the thickness of the wall falls outside of acceptable tolerances, installation of the window or door can be problematic. This problem occurs with some frequency in new construction due to variations in the thicknesses and planarity of studs, sheet rock, and other components of the wall. This problem becomes particularly acute when installing new fenestration products in older buildings, which typically have a much wider variance in wall thicknesses depending on a number of factors, including the age and geographical location of the building thicknesses depending on a number of factors, including the age and geographical location of the building.
Some manufacturers have attempted to address the variation in wall thicknesses in new construction, with varying degrees of success. Baier et al., U.S. Pat. No. 5,791,104, the entirety of which is incorporated herein by reference, suggests a jamb extension assembly for doors and windows. This assembly employs a multicomponent frame that can be assembled from multiple components by a manufacturer. The frame includes a jamb extender receiving slot and a jamb. The jamb includes an extender flange formed of a thin sheet of synthetic material that is adapted to be snapped along preformed score lines to adjust the length of the extender flange. Variations in wall thicknesses are accommodated by adjusting the extender flange to the appropriate length by breaking off a portion of the extender flange along the appropriate score line. Unfortunately, this requires that a visible inner portion of the window unit be formed of a relatively thin, breakable sheet material. If the window is not perfectly rectangular, the jamb extender flange may not precisely align with the receiving slot. Particularly with larger window sizes, it can be difficult to shove the extender flange into the slot. Attempts to force the extender flange into the slot can cause the flange to break along the preformed score lines, largely defeating the cosmetic purpose of the jamb extender.
Adjustable jamb designs such as the one proposed by Baier et al. can be even more problematic in retrofit installations in existing buildings. After the Second World War, old-style wooden window frames were largely phased out in new home construction in the United States in favor of prefabricated aluminum frames. FIG. 1 schematically illustrates the basic structural design of such an aluminum frame 1. This aluminum frame 1 includes an inner portion 2 designed to mount within a xe2x80x9croughxe2x80x9d window housing 3 in the wall. The frame 1 also includes an outer portion 4, which typically has a width (e.g., about 19 millimeters) about the same as the width of the inner portion 2. The inner and outer portions 2 and 4, respectively, of the frame 1 are demarcated at a cross-sectional midpoint of the frame 1 by a nailing flange 5 that extends outwardly from the outside periphery of the frame 1 to secure the frame 1 to the window housing 3.
The prior art aluminum frames 1 were designed for installation into window housings 3 made up of 2xc3x974 inch (50 mmxc3x97100 mm) studs 6, or like materials, covered externally by a sheathing, insulating, or subsiding layer 7 and, occasionally, a subsill, jamb and header 12a. To install the frame 1, the frame 1 was partially inserted into the window housing 3 so that the inner portion 2 overlapped the subsill, jamb and header 12a and partially overlapped the stud 6. To secure the frame 1 within the window housing 3, a nail 10 was then driven through the nailing flange 5 into the stud 6.
After installation of the aluminum frame 1 was thus completed, the outside of the window housing 3 was xe2x80x9cfinishedxe2x80x9d by securing a layer of siding material 11, such as shingles, to the outer surface of the subsiding layer 7, abutted against an undersurface of the outer portion 4 of the frame 1 to cover the nailing flange 5. The inside of the window housing 3 was finished by securing an inner lining 12b, such as sheet rock or paneling, over the stud 6 and optional subsill, jamb, and header 12a of the window housing 3. This inner lining 12b was abutted against the inside face of the window housing 3 to form a finished interior sill. Sheet rock 12c or the like was used to finish the interior.
Aluminum window frames continued to be widely used in new home construction in the United States throughout the 1970s, after which they began to be phased out in favor of more energy-efficient, durable, and aesthetically appealing double-paned, extruded plastic frames. Along with this new construction boom, a large replacement market for modern plastic frames has developed in recent years. Accordingly, millions of households across the United States and elsewhere have elected to replace existing aluminum frames with more durable, attractive, and energy-efficient plastic frames.
There are three common methods for retrofit installation of modern plastic window frames into finished window housings 3 originally designed for the prior art aluminum frames 1. The most common method is to simply remove the old frame 1 in its entirety and install the replacement frame in its place (e.g., with an inner portion of the replacement frame seated atop the subsiding layer 7 and a portion of the stud 6 abutting, but not overlapping the inner lining 12b) without modifying the finished housing. However, modern, double-paned plastic window frames are considerably wider (one standard width is about 80 mm) than the aluminum frames (variable, but approximately 38 mm). This increased width is necessary to accommodate the double glazing panels and insulating airspace between the panels. Therefore, when modern plastic frames are installed according to the above method, the frame protrudes outwardly far beyond the window housing, creating an awkward external appearance and causing a structurally undesirable weight distribution. Such installation methods, although widely practiced, are discouraged or prohibited by building codes and special utility grants.
A second method for retrofit installation of modern, double-paned window frames into finished window housings 3 includes removing the old aluminum frame 1 and mounting the new frame on top of the existing subsill, jamb, and header 12a of the window housing 3. Under this alternative method, the installer must trim back the lining 12b to accommodate a deeper inset and a more flush external appearance of the frame. If the frame 1 is mounted on top of the subsill, jamb, and header 12a, the installer must trim out the outer portion (i.e., the subsill, jamb, and header 12a and subsiding layer 7) of the window housing 3 with wood or other filler material to eliminate gaps between the periphery of the new frame and the inner lining 12b and subsiding layer 7. This trimming, which typically requires a skilled carpenter at the building site, is expensive and can account for a large portion of the total retrofit installation costs.
As a third method, some installers apparently are retrofitting modern vinyl frames on top of the existing aluminum main frame by first removing the existing sash and fixed lite, then positioning the new frame in the resulting opening. Extensive on-site trimming with wood is still required to cover the subsill, jamb, and header 12b because of the variable width of the existing aluminum main frames 1. Typically, the new vinyl frame is butt-jointed to a piece of wood custom ripped on-site to the current width to hide the existing frame 1. Additional trim pieces must be custom cut to cover gaps between the new butt-jointed liner and the existing liner, as well as for the outside of the new window. These activities are extremely labor-intensive and require skilled carpenters, adding significantly to the cost of window renovation.
Retrofitting window frames into stucco-finished window openings can be complicated by difficulties in removing the stucco siding layer covering the nailing flange of the original frame to allow the original frame to be removed. Unlike shingles and other siding materials, stucco must be chipped away from the nailing flange and cannot be replaced easily after removal of the old frame. Due to the high cost of repairing stucco, it is common practice to leave the original aluminum frame in place and to mount the replacement frame over the original frame. This requires removing any nailing flanges from the replacement frame and mounting the frame within the opening bounded by the original frame after its glazing panel and any cross-pieces have been torn out.
However, the increased width of the replacement frame requires a deep inset so that the replacement frame can extend inward well beyond the inner face of the existing aluminum frame. This mounting arrangement forms a gap between the inner portion of the replacement frame and the lining portion of the original window housing. In current practice, this gap is trimmed with wood or other material cut on-site to fill or mask the gap, resulting in a significant increase in total retrofit installation costs. An additional drawback to this method is that the replacement frame, seated within the aperture defined by the original frame, causes extensive loss of site and daylight by narrowing the glazing panel aperture height and width. To avoid an unsightly external appearance of the window, the frame also must be modified by a special flange extending peripherally from the outside of the frame to cover the outer face of the original aluminum frame.